1. Field of the Invention
The present invention concerns a diaphragm valve for controlling a flow of gaseous or liquid fluid and, particularly, to direct such flow from at least one port of the valve to at least one other port of the valve.
2. Related Art
WO 95/00782, by the present inventor, describes such a diaphragm valve including a valve housing having a substantially circular valve chamber, into which opens a central channel and on each side thereof a first side channel and a second side channel. Each side channel has an external connection for fluid and is separated from the central channel by means of a respective one of two substantially parallel valve seat means extending like chords across the valve chamber. Each valve seat means provides a substantially linear valve seat for an elastic diaphragm. The diaphragm is adapted to be brought into and away from sealing contact with at least one of the valve seat means. Two individually operable control means are adapted both to press a respective linear portion of the diapghragm against a respective valve seat, thereby to shut passage of fluid between the central channel and a respective side channel, and to positively raise a respective portion of the diaphragm off a respective one of the valve seat, thereby to open a flow passage between the central channel and the respective side channel.
This prior art three-way/three-port diaphragm valve proved to operate extremely well. There was, however, a desire to convert it to a 4-way/4-port valve, i.e., a valve for mixing three flows, or, to direct flow from one external connection (inlet port) to one or more of three other external connections (outlet ports).
That was accomplished by a first development of the valve as initially stated. This first development is described in WO 97/17558 by the same inventor. In the diaphragm valve according to the first development, the valve housing is provided with a second substantially circular valve chamber, into which opens a fourth channel having an external connection for fluid and which communicates with the central channel through an opening in the valve housing. A second elastic diaphragm is provided and is adapted to be brought into and away from sealing engagement with a third valve seat means provided in the second valve chamber. A third control means is arranged both to press the second diaphragm against the third valve seat means, thereby to shut passage of fluid between the fourth channel and the central channel, and to release the diaphragm from its engagement with the third valve seat means, thereby to open passage of fluid between the fourth channel and the central channel.
Also this valve has proven to satisfactory fulfil its objects.
Common to the two prior art valves mentioned is a central channel having direct communication with an associated port. Consequently, this port becomes involved also in fluid transfer between the remaining two ports in the valve according to WO 95/00782 and between any combination of two of the remaining three ports in the valve according to WO 97/17558.